Rectification circuit

Abstract

In the present invention, a first control circuit (11) turns on a first switching element (Q1) when a negative voltage is applied, and generates a first control signal for turning off the transistor (Q1) when a positive voltage is applied. A second control circuit (12) turns on a second switching element (Q2) when a negative voltage is applied, and generates a second control signal for turning off the transistor (Q2) when a positive voltage is applied. When a positive voltage is applied to the first switching element (Q1), the first control circuit (11) supplies the second control circuit (12) with power for generating the second control signal. When a positive voltage is applied to the second switching element (Q2), the second control circuit (12) supplies the first control circuit (11) with power for generating the first control signal.

Description

rectifier circuit

[0001] The present disclosure relates to a rectifier circuit, a control method for the rectifier circuit, and a power system.

[0002] Power conversion devices used to operate DC loads using commercial AC power often include a rectifier circuit and a DC / DC conversion circuit, or a rectifier circuit, a power factor correction circuit, and a DC / DC conversion circuit. Among these, the rectifier circuit typically includes a bridge circuit of multiple diodes. To reduce losses, the rectifier circuit may also include transistors instead of diodes. Generally, losses due to the on-resistance of a transistor are smaller than losses due to the forward voltage of a diode. Therefore, by turning a transistor on and off depending on the polarity of the input voltage, a rectifier circuit that can operate with lower losses than a diode bridge circuit can be realized. A rectifier circuit that includes such transistors is called an "active rectifier circuit" or a "synchronous rectifier circuit."

[0003] For example, Patent Document 1 discloses a rectifier circuit including a bridge circuit of a plurality of MOS transistors.

[0004] U.S. Pat. No. 10,756,645

[0005] The rectifier circuit of Patent Document 1 includes a plurality of control circuits corresponding to the plurality of transistors, respectively, to turn the transistors on and off according to the polarity of the input voltage. The rectifier circuit of Patent Document 1 also includes a plurality of capacitors corresponding to the plurality of control circuits, respectively, to operate the control circuits without providing an additional external power supply. Each capacitor is charged by the voltage across the transistor when no current flows through the transistor, and supplies power to the control circuit.

[0006] A power conversion device including a rectifier circuit may receive not only AC power but also DC power. A rectifier circuit such as that disclosed in Patent Document 1 can charge each capacitor and supply power to each control circuit when AC power is input, i.e., when the polarity of the voltage applied to each transistor changes periodically. However, when DC power is input, i.e., when the polarity of the voltage applied to each transistor does not change, the rectifier circuit such as that disclosed in Patent Document 1 cannot charge some capacitors, and therefore does not supply power to the corresponding control circuit. As a result, transistors that should be turned on cannot be turned on, and the rectifier circuit cannot operate with low loss. Therefore, a rectifier circuit that can operate with low loss not only when AC power is input but also when DC power is input is desired.

[0007] An object of the present disclosure is to provide a rectifier circuit that can operate with lower loss than a diode bridge circuit, and that can operate with low loss not only when AC power is input but also when DC power is input. Another object of the present disclosure is to provide a control method for such a rectifier circuit and a power system including such a rectifier circuit.

[0008] A rectifier circuit according to a first aspect of the present disclosure comprises: first and second input terminals, first and second output terminals, first to fourth switching elements, and first and second control circuits; the first switching element is connected between the first input terminal and the first output terminal; the second switching element is connected between the second input terminal and the first output terminal; the third switching element is connected between the first input terminal and the second output terminal; and the fourth switching element is connected between the second input terminal and the second output terminal; the first and second switching elements are transistors; a positive or negative voltage is applied to the first and second switching elements with respect to a potential of the first output terminal; and the first control circuit generates a first control signal for turning on the first switching element when a negative voltage is applied to the first switching element and for turning off the first switching element when a positive voltage is applied to the first switching element. The second control circuit generates a second control signal for turning on the second switching element when a negative voltage is applied to the second switching element and for turning off the second switching element when a positive voltage is applied to the second switching element; the first control circuit supplies power to the second control circuit for generating the second control signal when a positive voltage is applied to the first switching element; and the second control circuit supplies power to the first control circuit for generating the first control signal when a positive voltage is applied to the second switching element.

[0009] This configuration makes it possible to provide a rectifier circuit that can operate with lower loss than a diode bridge circuit, and that can operate with low loss not only when AC power is input, but also when DC power is input.

[0010] According to a rectifier circuit according to a second aspect of the present disclosure, in the rectifier circuit according to the first aspect, the rectifier circuit further includes a capacitor connected to both the first and second control circuits, the capacitor temporarily storing power for generating the first and second control signals.

[0011] With this configuration, the power stored in the capacitor can be shared by the first and second control circuits.

[0012] According to a rectifier circuit according to a third aspect of the present disclosure, in the rectifier circuit according to the first aspect, the third switching element is a first diode having a forward direction from the first input terminal to the second output terminal, and the fourth switching element is a second diode having a forward direction from the second input terminal to the second output terminal.

[0013] This configuration allows the rectifier circuit to operate without providing an additional external power supply.

[0014] According to a fourth aspect of the present disclosure, in the rectifier circuit of the first aspect, the third and fourth switching elements are transistors, a positive or negative voltage is applied to the third switching element with respect to the potential of the first input terminal, and a positive or negative voltage is applied to the fourth switching element with respect to the potential of the second input terminal, and the rectifier circuit further includes: a third control circuit that generates a third control signal for turning on the third switching element when a negative voltage is applied to the third switching element and for turning off the third switching element when a positive voltage is applied to the third switching element; a fourth control circuit that generates a fourth control signal for turning on the fourth switching element when a negative voltage is applied to the fourth switching element and for turning off the fourth switching element when a positive voltage is applied to the fourth switching element; a first power supply that supplies power to the third control circuit for generating the third control signal; and a second power supply that supplies power to the fourth control circuit for generating the fourth control signal.

[0015] This configuration can reduce losses more than when the third and fourth switching elements are diodes.

[0016] A power system according to a fifth aspect of the present disclosure includes: a rectifier circuit according to one of the first to fourth aspects; a power conversion circuit that receives output power from the rectifier circuit and converts at least one of voltage, frequency, and power factor; and a load device that operates using the output power from the power conversion circuit.

[0017] This configuration makes it possible to provide a power system that is a rectifier circuit that can operate with lower loss than a diode bridge circuit and that can operate not only when AC power is input, but also when DC power is input.

[0018] According to a sixth aspect of the present disclosure, there is provided a control method for a rectifier circuit including first and second input terminals, first and second output terminals, first to fourth switching elements, and first and second control circuits, wherein the first switching element is connected between the first input terminal and the first output terminal, the second switching element is connected between the second input terminal and the first output terminal, the third switching element is connected between the first input terminal and the second output terminal, and the fourth switching element is connected between the second input terminal and the second output terminal, the first and second switching elements are transistors, and a positive or negative voltage is applied to the first and second switching elements with respect to a potential of the first output terminal, and the control method for the rectifier circuit includes generating, by the first control circuit, a first control signal for turning on the first switching element when a negative voltage is applied to the first switching element, and for turning off the first switching element when a positive voltage is applied to the first switching element; The control circuit includes generating, by the second control circuit, a second control signal for turning on the second switching element when a negative voltage is applied to the second switching element and for turning off the second switching element when a positive voltage is applied to the second switching element; supplying power for generating the second control signal from the first control circuit to the second control circuit when a positive voltage is applied to the first switching element; and supplying power for generating the first control signal from the second control circuit to the first control circuit when a positive voltage is applied to the second switching element.

[0019] This configuration makes it possible to provide a rectifier circuit that can operate with lower loss than a diode bridge circuit, and a control method for a rectifier circuit that can operate with low loss not only when AC power is input, but also when DC power is input.

[0020] According to one aspect of the present disclosure, it is possible to provide a rectifier circuit that can operate with lower loss than a diode bridge circuit, and that can operate with lower loss not only when AC power is input, but also when DC power is input.

[0021] 9 is a block diagram showing the configuration of a power system including a rectifier circuit 2 according to a first embodiment. It is a circuit diagram showing the configuration of the rectifier circuit 2 of FIG. 1. It is a circuit diagram showing the configuration of a control circuit 11 of FIG. 2. It is a circuit diagram showing the configuration of a rectifier circuit 2A according to a comparative example. It is a circuit diagram for explaining the operation of the control circuit 11 of FIG. 4. It is a timing chart showing changes in voltage Vds1, voltage Vgs1, and current Id1 of FIG. 5. It is a timing chart showing changes in voltages Vds1, Vq21, Va1, and Vc1 of FIG. 5. It is a circuit diagram for explaining the current that flows when a DC power supply device 1dc is connected to the rectifier circuit 2A of FIG. 4. It is a circuit diagram for explaining the operation of the rectifier circuit 2 of FIG. 2. It is a timing chart showing changes in voltages Vds1, Vds2, Vq21, Vq22, Vc0, Vgs1, and Vgs2 of FIG. 3 is a timing chart showing changes in voltages Vds1, Vds2, Vq21, Vq22, Vc0, Vgs1, and Vgs2 when a DC power supply device 1dc is connected to the rectifier circuit 2 of Fig. 2. FIG. 4 is a graph for explaining the operation of the control circuits 11 and 12 of Fig. 2 to control charging to the capacitor C0 based on the charging voltage Vc0 of the capacitor C0. FIG. 5 is a circuit diagram showing the configuration of a part of a rectifier circuit 2B according to a second embodiment. FIG. 6 is a circuit diagram showing the configuration of a rectifier circuit 2C according to a third embodiment.

[0022] Hereinafter, an embodiment according to one aspect of the present disclosure will be described with reference to the drawings. In each drawing, the same reference numerals indicate similar components.

[0023] [First embodiment] [Configuration of first embodiment] Fig. 1 is a block diagram showing the configuration of a power system including a rectifier circuit 2 according to a first embodiment. The power system in Fig. 1 includes a power supply device 1, a rectifier circuit 2, a power factor correction circuit 3, a DC / DC conversion circuit 4, and a load device 5.

[0024] The power supply device 1 supplies AC power or DC power.

[0025] When AC power is supplied from the power supply device 1, the rectifier circuit 2 rectifies and smoothes the AC power into DC power. When DC power is supplied from the power supply device 1, the rectifier circuit 2 outputs the DC power as is.

[0026] The power factor correction circuit 3 improves the power factor of the DC power output from the rectifier circuit 2 (i.e., brings it closer to "1").

[0027] The DC / DC conversion circuit 4 converts the first DC voltage output from the power factor correction circuit 3 into a second DC voltage.

[0028] The load device 5 operates using the DC power output from the DC / DC conversion circuit 4 and performs some kind of work.

[0029] The power factor correction circuit 3 and the DC / DC conversion circuit 4 are an example of a power conversion circuit that receives the output power of the rectifier circuit 2 and converts at least one of the voltage, frequency, and power factor.

[0030] Fig. 2 is a circuit diagram showing the configuration of the rectifier circuit 2 of Fig. 1. The rectifier circuit 2 includes transistors Q1 and Q2, diodes D1 and D2, control circuits 11 and 12, and capacitors C0 and C10. The rectifier circuit 2 also has input terminals P1 and P2 connected to the power supply device 1 and output terminals P3 and P4 connected to the power factor correction circuit 3. The example of Fig. 2 shows a case where the input terminals P1 and P2 are connected to the AC power supply device 1ac.

[0031] The transistor Q1 is connected between the input terminal P1 and the output terminal P4. The transistor Q2 is connected between the input terminal P2 and the output terminal P4. The transistors Q1 and Q2 are power transistors such as metal-oxide-semiconductor field-effect transistors (MOSFETs) or reverse-conducting insulated gate bipolar transistors (RC-IGBTs). In this embodiment, a case will be described in which the transistors Q1 and Q2 are MOSFETs. The transistors Q1 and Q2 have body diodes or diodes connected externally in parallel. In this case, the body diode of the transistor Q1 has a forward direction (i.e., a direction from the anode to the cathode) from the output terminal P4 toward the input terminal P1, and the body diode of the transistor Q2 has a forward direction from the output terminal P4 toward the input terminal P2.

[0032] The diode D1 is connected between the input terminal P1 and the output terminal P3, and has a forward direction from the input terminal P1 to the output terminal P3. The diode D2 is connected between the input terminal P2 and the output terminal P3, and has a forward direction from the input terminal P2 to the output terminal P3.

[0033] The transistors Q1 and Q2 and the diodes D1 and D2 are an example of switching elements that form a bridge circuit.

[0034] Control circuits 11 and 12 turn transistors Q1 and Q2 on and off depending on the polarity of the input voltage. A positive or negative voltage is applied to transistors Q1 and Q2 relative to the potential of output terminal P4. Control circuit 11 generates a first control signal to turn transistor Q1 on when a negative voltage is applied to transistor Q1 and to turn transistor Q1 off when a positive voltage is applied to transistor Q1. Control circuit 12 generates a second control signal to turn transistor Q2 on when a negative voltage is applied to transistor Q2 and to turn transistor Q2 off when a positive voltage is applied to transistor Q2. Control circuit 11 supplies power to control circuit 12 for generating the second control signal when a positive voltage is applied to transistor Q1. Control circuit 12 supplies power to control circuit 11 for generating the first control signal when a positive voltage is applied to transistor Q2.

[0035] The control circuits 11, 12 may be existing products commercially available as control circuits for active rectifier circuits, for example, AOZ2700CI sold by Alpha and Omega Semiconductor.

[0036] The capacitor C0 is connected to both the control circuits 11 and 12 and temporarily stores power for generating the first and second control signals.

[0037] The capacitor C10 is connected between the output terminals P3 and P4 and smoothes the output voltage of the rectifier circuit 2.

[0038] Fig. 3 is a circuit diagram showing the configuration of the control circuit 11 of Fig. 2. The control circuit 11 includes a transistor Q21, a diode D21, an internal control circuit 21-1, a reference voltage circuit 22-1, and a comparator 23-1.

[0039] The transistor Q21 is, for example, a depletion-type MOSFET. The drain of the transistor Q21 is connected to the drain of the transistor Q1, and the source of the transistor Q21 is connected to the anode of a diode D21. The cathode of the diode D21 is grounded via a capacitor C0.

[0040] Capacitor C0 is charged through transistor Q21 and diode D21 when a positive voltage is applied to transistor Q1.

[0041] The internal control circuit 21-1 controls the channel resistance of the transistor Q21 in accordance with the drain-source voltage of the transistor Q1. The internal control circuit 21-1 includes a Zener diode ZD21 and a resistor R21. The anode of the Zener diode ZD21 is connected to the gate of the transistor Q21, and the cathode of the Zener diode ZD21 is grounded. The resistor R21 is connected between the anode of the Zener diode ZD21 and the source of the transistor Q21.

[0042] The reference voltage circuit 22-1 supplies one of two reference voltages to the comparator 23-1 in response to the output signal of the comparator 23-1. The reference voltage circuit 22-1 includes reference voltage sources Ea1 and Eb1 and a multiplexer MUX1. The reference voltage source Ea1 generates a first reference voltage Vrefa, and the reference voltage source Eb1 generates a second reference voltage Vrefb. For example, the second reference voltage Vrefb is set to a value higher than the first reference voltage Vrefa. For example, when the control circuits 11 and 12 are AOZ2700CI, Vrefa=-105 mV and Vrefb=1 mV. The multiplexer MUX1 supplies the reference voltage Vrefa to the comparator 23-1 when the voltage of the output signal of the comparator 23-1 is at a low level, and supplies the reference voltage Vrefb to the comparator 23-1 when the voltage of the output signal of the comparator 23-1 is at a high level. By using the two reference voltages Vrefa and Vrefb, the output signal of the comparator 23-1 has hysteresis, making it less likely that unwanted switching operation of the transistor Q1 will occur.

[0043] The potential of the source of transistor Q21 is input to the inverting input terminal of comparator 23-1, and the reference voltage Vrefa or Vrefb output from reference voltage circuit 22-1 is input to the non-inverting input terminal of comparator 23-1. The comparator 23-1 operates by receiving power from capacitor C0. The output signal of comparator 23-1 is applied to the gate of transistor Q1.

[0044] The charging voltage of the capacitor C0 is set to a value equal to or lower than the rated voltage of the comparator 23-1 and equal to or higher than the gate threshold voltage of the transistor Q1. For example, when the control circuits 11 and 12 are AOZ2700CI, the charging voltage of the capacitor C0 is set to 13 to 17V.

[0045] Transistor Q21 is provided to prevent an overvoltage from being applied to comparator 23-1. Specifically, when the drain-source voltage of transistor Q1 is low, internal control circuit 21-1 controls transistor Q21 to lower the channel resistance. As a result, the drain-source voltage of transistor Q1 is essentially input directly to the non-inverting input terminal of comparator 23-1. On the other hand, when the drain-source voltage of transistor Q1 is high, internal control circuit 21-1 controls transistor Q21 to increase the channel resistance. As a result, the voltage drop across transistor Q21 increases, preventing a voltage exceeding the rated voltage from being applied to comparator 23-1. For example, if an AC voltage having an effective value of 230 V and a maximum value of 230 × √2 = 325 V is input and the voltage applied to comparator 23-1 needs to be 18 V or less, transistor Q21 is controlled so that the drain-source voltage drop is 325 V - 18 V = 307 V.

[0046] Control circuit 12 is also configured in the same manner as control circuit 11. Control circuit 12 controls transistor Q2 in the same manner as control circuit 11 controls transistor Q1. Furthermore, when a positive voltage is applied to transistor Q2, control circuit 12 charges capacitor C0 in the same manner as control circuit 11 charges capacitor C0.

[0047] Comparative Example Before describing the operation of the rectifier circuit 2 according to this embodiment, the configuration and operation of a rectifier circuit 2A according to a comparative example will be described.

[0048] 4 is a circuit diagram showing the configuration of a rectifier circuit 2A according to a comparative example. Instead of the capacitor C0 in FIG. 2, the rectifier circuit 2A includes capacitors C1 and C2 connected to control circuits 11 and 12, respectively. When a positive voltage is applied to transistor Q1, the control circuit 11 temporarily stores in capacitor C1 power for generating a first control signal that turns transistor Q1 on and off. When a positive voltage is applied to transistor Q2, the control circuit 12 temporarily stores in capacitor C2 power for generating a second control signal that turns transistor Q2 on and off.

[0049] 5 is a circuit diagram for explaining the operation of the control circuit 11 of FIG. 4. The control circuit 11 of FIG. 4 is configured similarly to the control circuit 11 of FIG. 3, except that the control circuit 11 is connected to a separate capacitor C1 instead of being connected to the common capacitor C0 with the control circuit 12. Vds1 represents the drain-source voltage of transistor Q1. Vgs1 represents the gate-source voltage of transistor Q1. Id1 represents the drain current of transistor Q1. Vq21 represents the drain-source voltage of transistor Q21. Va1 represents the voltage at node Na between transistor Q21 and diode D21. Vc1 represents the charging voltage of capacitor C1.

[0050] FIG. 6 is a timing chart showing changes in the voltage Vds1, the voltage Vgs1, and the current Id1 in FIG.

[0051] When transistor Q1 transitions from off to on, control circuit 11 controls transistor Q1 as follows: When a negative voltage is applied to transistor Q1 and transistor Q1 is off, current flows from the anode to the cathode of the body diode of transistor Q1. A voltage drop across the body diode of transistor Q1 generates a negative voltage Vds1 between the drain and source of transistor Q1. At time t1, when voltage Vds1 becomes equal to or lower than reference voltage Vrefa, comparator 23-1 transitions its output signal (i.e., voltage Vgs1) from low to high, turning on transistor Q1.

[0052] On the other hand, when transistor Q1 transitions from on to off, control circuit 11 controls transistor Q1 as follows: When transistor Q1 is on, a negative voltage Vds1 is generated between the drain and source of transistor Q1 due to the on-resistance of transistor Q1 and the current Id1 flowing through it. As the current flowing through transistor Q1 decreases, the drain-source voltage of transistor Q1 increases and approaches 0 V. At time t2, when voltage Vds1 becomes equal to or greater than reference voltage Vrefb, comparator 23-1 transitions its output signal (i.e., voltage Vgs1) from high to low, turning off transistor Q1.

[0053] 7 is a timing chart showing the changes in voltages Vds1, Vq21, Va1, and Vc1 in FIG. 5. Vp indicates the peak value of the input AC voltage, i.e., the voltage applied to transistor Q1. Vap indicates the peak value of voltage Va1 at node Na. Vf indicates the forward voltage of diode D21.

[0054] The control circuit 11 controls the capacitor C1 as follows. During the period from time t11 to t14 in FIG. 7, the transistor Q1 is in a non-conductive state; that is, a positive voltage is applied to the transistor Q1, and no current flows through either the channel or the body diode of the transistor Q1. During this period, if the drain-source voltage Vds1 of the transistor Q1 is high, for example, if it exceeds the rated voltage of the comparator 23-1, the internal control circuit 21-1 controls the transistor Q21 to increase the channel resistance, as described above. As a result, even if the voltage drop across the transistor Q21 increases and the voltage Vds1 exceeds the rated voltage of the comparator 23-1, the voltage Va1 at the node Na is maintained at a constant voltage equal to or lower than the rated voltage of the comparator 23-1. The capacitor C1 is charged by the voltage Va1 at the node Na via the diode D21. Therefore, the charging voltage Vc1 of the capacitor C1 is the voltage Va1 at the node Na minus the forward voltage Vf of the diode D21. When the polarity of the input AC voltage is reversed and a negative voltage is applied to the transistor Q1, the charge stored in the capacitor C1 is consumed to turn on the transistor Q1, and the charge voltage Vc1 gradually decreases.

[0055] The control circuit 11 turns off the transistor Q1 and charges the capacitor C1 during the positive half cycle of the input AC voltage, and turns on the transistor Q1 during the negative half cycle of the input AC voltage.

[0056] 4 is configured similarly to the control circuit 11 and operates similarly to the control circuit 11. The control circuit 12 turns off the transistor Q2 and charges the capacitor C2 during the negative half cycle of the input AC voltage, and turns on the transistor Q2 during the positive half cycle of the input AC voltage.

[0057] 4, when AC power is input to the rectifier circuit 2A, a positive voltage is alternately applied to the transistors Q1 and Q2, and the capacitors C1 and C2 are alternately charged. Therefore, the control circuits 11 and 12 can obtain power from the capacitors C1 and C2, respectively, to generate control signals that turn on and off the transistors Q1 and Q2.

[0058] FIG. 8 is a circuit diagram illustrating the current flowing when the DC power supply 1dc is connected to the rectifier circuit 2A of FIG. 4. When DC power is input to the rectifier circuit 2A of FIG. 4, a positive voltage is always applied to one of the transistors Q1 and Q2, and a negative voltage is always applied to the other of the transistors Q1 and Q2. In the example of FIG. 8, a negative voltage is always applied to the transistor Q2. Therefore, the capacitor C2 cannot be charged, and the control circuit 12 cannot obtain power from the capacitor C2 to generate a control signal for turning the transistor Q2 on and off. In this case, the current flows through the body diode of the transistor Q2, resulting in greater loss than when the current flows through the channel of the transistor Q2.

[0059] In contrast, the rectifier circuit 2 according to this embodiment can operate with low loss not only when AC power is input, but also when DC power is input, as will be described below.

[0060] 9 is a circuit diagram for explaining the operation of the rectifier circuit 2 of FIG. 2. The control circuit 12 includes a transistor Q22, a diode D22, an internal control circuit 21-2, a reference voltage circuit 22-2, and a comparator 23-2. These components of the control circuit 12 are configured similarly to the corresponding components of the control circuit 11 and operate similarly.

[0061] Vds1 indicates the drain-source voltage of transistor Q1. Vgs1 indicates the gate-source voltage of transistor Q1. Vq21 indicates the drain-source voltage of transistor Q21. Ic1 indicates the charging current of capacitor C0 when a positive voltage is applied to transistor Q1. Vds2 indicates the drain-source voltage of transistor Q2. Vgs2 indicates the gate-source voltage of transistor Q2. Vq22 indicates the drain-source voltage of transistor Q22. Ic2 indicates the charging current of capacitor C0 when a positive voltage is applied to transistor Q2. Vc0 indicates the charging voltage of capacitor C0.

[0062] Fig. 10 is a timing chart showing changes in voltages Vds1, Vds2, Vq21, Vq22, Vc0, Vgs1, and Vgs2 in Fig. 9. When AC power is input, control circuits 11 and 12 control capacitor C0 as follows.

[0063] During the period from t21 to t24 in Figure 10, i.e., during the positive half-cycle of the input AC voltage, transistor Q1 is in a non-conductive state. That is, a positive voltage is applied to transistor Q1, and no current flows through either the channel or the body diode of transistor Q1. During this period, if the drain-source voltage Vds1 of transistor Q1 is high, for example, if it exceeds the rated voltage of comparator 23-1, internal control circuit 21-1 controls transistor Q21 to increase the channel resistance. As a result, even if the voltage drop across transistor Q21 increases and voltage Vds1 exceeds the rated voltage of comparator 23-1, the voltage at the node between transistor Q21 and diode D21 is maintained at a constant voltage below the rated voltage of comparator 23-1. Capacitor C0 is charged via transistor Q21 and diode D21. Furthermore, when the drain-source voltage Vds2 of the transistor Q2 becomes equal to or lower than the reference voltage Vrefa, the comparator 23-2 consumes the charge stored in the capacitor C0, transitions the output signal (i.e., the voltage Vgs2) from low level to high level, and turns on the transistor Q2.

[0064] During the period from t24 to t27 in Figure 10, i.e., during the negative half-cycle of the input AC voltage, transistor Q2 is in a non-conductive state. That is, a positive voltage is applied to transistor Q2, and no current flows through either the channel or the body diode of transistor Q2. During this period, if the drain-source voltage Vds2 of transistor Q2 is high, for example, if it exceeds the rated voltage of comparator 23-2, internal control circuit 21-2 controls transistor Q22 to increase the channel resistance. As a result, even if the voltage drop across transistor Q22 increases and voltage Vds2 exceeds the rated voltage of comparator 23-2, the voltage at the node between transistor Q22 and diode D22 is maintained at a constant voltage below the rated voltage of comparator 23-2. Capacitor C0 is charged via transistor Q22 and diode D22. Furthermore, when the drain-source voltage Vds1 of the transistor Q1 becomes equal to or lower than the reference voltage Vrefa, the comparator 23-1 consumes the charge stored in the capacitor C0, transitions the output signal (i.e., the voltage Vgs1) from low level f to high level, and turns on the transistor Q1.

[0065] 11 is a timing chart showing changes in voltages Vds1, Vds2, Vq21, Vq22, Vc0, Vgs1, and Vgs2 when the DC power supply 1dc is connected to the rectifier circuit 2 of FIG. 2. In the example of FIG. 11, a positive voltage is always applied to transistor Q1, and a negative voltage is always applied to transistor Q2. Capacitor C0 is charged by control circuit 11, so that control circuit 12 can obtain power from capacitor C0 to generate a control signal for turning transistor Q2 on and off.

[0066] During the positive half cycle of the input AC voltage, capacitor C0 is charged by current Ic1, and the charge stored in capacitor C0 is consumed by comparator 23-2 and the gate of transistor Q2. During the negative half cycle of the input AC voltage, capacitor C0 is charged by current Ic2, and the charge stored in capacitor C0 is consumed by comparator 23-1 and the gate of transistor Q1. The rectifier circuit 2 according to this embodiment uses the same control circuits 11 and 12 as those in the rectifier circuit 2A according to the comparative example, and can charge capacitor C0 and supply power to the control circuits 11 and 12 not only when AC power is input, but also when DC power is input.

[0067] FIG. 12 is a graph illustrating the operation of the control circuits 11 and 12 of FIG. 2 to control the charging of capacitor C0 based on the charging voltage Vc0 of capacitor C0. For example, if the control circuits 11 and 12 are AOZ2700CI, the AOZ2700CI is configured to control the charging according to the charging voltage Vc0 of capacitor C0. When the charging voltage Vc0 increases and reaches an upper threshold Vth1, e.g., 15.6 V, transistor Q21 is turned off and charging is stopped. This prevents unnecessary losses due to charging. When the charging voltage Vc0 decreases and reaches a lower threshold Vth2, e.g., 13 V, transistor Q21 is turned on, and capacitor C0 is again charged to the upper threshold Vth1. This operation is then repeated. Therefore, as shown in FIG. 12, the waveform of the charging voltage Vc0 contains ripple, but this has little effect on losses. In this way, even when existing products are used as the control circuits 11 and 12, a rectifier circuit can be provided that can operate with low loss not only when AC power is input, but also when DC power is input.

[0068] As described above, the rectifier circuit 2 according to the first embodiment is a rectifier circuit that can operate with lower loss than a diode bridge circuit, and can provide a rectifier circuit that can operate with low loss not only when AC power is input, but also when DC power is input.

[0069] The rectifier circuit 2 according to the first embodiment can reduce the number of capacitors compared to the rectifier circuit 2A according to the comparative example, thereby making it possible to reduce the size of the circuit and reduce costs.

[0070] The rectifier circuit 2 of the first embodiment can operate the control circuits 11 and 12 without providing an additional external power supply, thereby making it possible to make the circuit smaller and reduce costs compared to when an additional external power supply is provided.

[0071] 13 is a circuit diagram showing a partial configuration of a rectifier circuit 2B according to a second embodiment. The rectifier circuit 2B has a configuration in which the capacitor C0 is removed from the rectifier circuit 2 of FIG.

[0072] Ic11 denotes the current supplied from the control circuit 11 to the control circuit 12 when a positive voltage is applied to the transistor Q1. Ic12 denotes the current supplied from the control circuit 12 to the control circuit 11 when a positive voltage is applied to the transistor Q2. If the amount of power supplied from the control circuit 11 to the control circuit 12 is sufficiently greater than the amount of power consumed by the comparator 23-2 and the gate of the transistor Q2, and if the amount of power supplied from the control circuit 12 to the control circuit 11 is sufficiently greater than the amount of power consumed by the comparator 23-1 and the gate of the transistor Q1, the capacitor C0 in FIG. 2 may be omitted. During the positive half-cycle of the input AC voltage, the positive voltage applied to the transistor Q1 can directly drive the gates of the comparator 23-2 and the transistor Q2. During the negative half-cycle of the input AC voltage, the positive voltage applied to the transistor Q2 can directly drive the gates of the comparator 23-1 and the transistor Q1.

[0073] According to the rectifier circuit 2B of the second embodiment, the capacitor C0 is eliminated, thereby making it possible to simplify the circuit and reduce costs compared to the first embodiment.

[0074] 14 is a circuit diagram showing the configuration of a rectifier circuit 2C according to a third embodiment. The rectifier circuit 2C includes transistors Q1 to Q4, control circuits 11 to 14, voltage sources E33 and E34, diodes D33 and D34, and capacitors C0 and C10. In other words, the rectifier circuit 2C includes transistors Q3 and Q4, control circuits 13 and 14, voltage sources E33 and E34, and diodes D33 and D34, instead of the diodes D1 and D2 shown in FIG. 2.

[0075] Transistors Q3 and Q4 are power transistors similar to transistors Q1 and Q2.

[0076] Control circuits 13 and 14 are configured similarly to control circuit 11 in Fig. 3. However, control circuit 13 is connected to a voltage source E33 and a diode D33 instead of capacitor C0, and receives power from voltage source E33. Control circuit 14 is connected to a voltage source E34 and a diode D34 instead of capacitor C0, and receives power from voltage source E34.

[0077] Control circuits 13 and 14 turn transistors Q3 and Q4 on and off depending on the polarity of the input voltage. A positive or negative voltage is applied to transistor Q3 with respect to the potential of input terminal P1. A positive or negative voltage is applied to transistor Q4 with respect to the potential of input terminal P2. Control circuit 13 generates a third control signal to turn transistor Q3 on when a negative voltage is applied to transistor Q3 and to turn transistor Q3 off when a positive voltage is applied to transistor Q3. Control circuit 14 generates a fourth control signal to turn transistor Q4 on when a negative voltage is applied to transistor Q4 and to turn transistor Q4 off when a positive voltage is applied to transistor Q4.

[0078] The voltage source E33 supplies power for generating the third control signal to the control circuit 13 via the diode D33. The voltage source E34 supplies power for generating the fourth control signal to the control circuit 14 via the diode D34.

[0079] The rectifier circuit 2C according to the third embodiment includes transistors Q3 and Q4 instead of the diodes D1 and D2 in FIG. 2, and therefore can reduce losses more than in the rectifier circuit 2 in FIG.

[0080] [Other Embodiments] Although the embodiments of the present disclosure have been described above in detail, the above description is merely an example of the present disclosure in every respect. It goes without saying that various improvements and modifications can be made without departing from the scope of the present disclosure. For example, the following modifications are possible. Note that, in the following, the same reference numerals are used for components similar to those in the above embodiment, and descriptions of the same points as those in the above embodiment are omitted as appropriate. The following modifications can be combined as appropriate.

[0081] The power system may include a DC / AC inverter instead of the DC / DC conversion circuit 4, and may be connected to a load device that operates on AC power instead of the load device 5 that operates on DC power. The DC / AC inverter is an example of a power conversion circuit that receives the output power of the rectifier circuit 2 and converts the frequency.

[0082] Summary of the Embodiments An electrical device according to each aspect of the present disclosure may be expressed as follows.

[0083] According to one aspect of the present disclosure, the rectifier circuits 2, 2B, and 2C include first and second input terminals P1 and P2, first and second output terminals P4 and P3, first to fourth switching elements, and first and second control circuits 11 and 12. The first switching element Q1 is connected between the first input terminal P1 and the first output terminal P4. The second switching element Q2 is connected between the second input terminal P2 and the first output terminal P4. The third switching element is connected between the first input terminal P1 and the second output terminal P3. The fourth switching element is connected between the second input terminal P2 and the second output terminal P3. The first and second switching elements Q1 and Q2 are transistors. A positive or negative voltage is applied to the first and second switching elements Q1 and Q2 with respect to the potential of the first output terminal P4. The first control circuit 11 generates a first control signal for turning on the first switching element Q1 when a negative voltage is applied to the first switching element Q1 and for turning off the first switching element Q1 when a positive voltage is applied to the first switching element Q1. The second control circuit 12 generates a second control signal for turning on the second switching element Q2 when a negative voltage is applied to the second switching element Q2 and for turning off the second switching element Q2 when a positive voltage is applied to the second switching element Q2. The first control circuit 11 supplies power to the second control circuit 12 for generating the second control signal when a positive voltage is applied to the first switching element Q1. The second control circuit 12 supplies power to the first control circuit 11 for generating the first control signal when a positive voltage is applied to the second switching element Q2.

[0084] According to one aspect of the present disclosure, the rectifier circuit 2 may further include a capacitor C0 connected to both the first and second control circuits 11, 12, which temporarily stores power for generating the first and second control signals.

[0085] According to one aspect of the present disclosure, the third switching element may be a first diode D1 having a forward direction from the first input terminal P1 to the second output terminal P3, and the fourth switching element may be a second diode D2 having a forward direction from the second input terminal P2 to the second output terminal P3.

[0086] According to one aspect of the present disclosure, the third and fourth switching elements may be transistors Q3 and Q4. In this case, a positive or negative voltage is applied to the third switching element Q3 with respect to the potential of the first input terminal P1. A positive or negative voltage is applied to the fourth switching element Q4 with respect to the potential of the second input terminal P2. The rectifier circuit 2 further includes a third control circuit 13 that generates a third control signal for turning on the third switching element Q3 when a negative voltage is applied to the third switching element Q3 and for turning off the third switching element Q3 when a positive voltage is applied to the third switching element Q3, a fourth control circuit 14 that generates a fourth control signal for turning on the fourth switching element Q4 when a negative voltage is applied to the fourth switching element Q4 and for turning off the fourth switching element Q4 when a positive voltage is applied to the fourth switching element Q4, a first power supply E33 that supplies power to the third control circuit for generating the third control signal, and a second power supply E34 that supplies power to the fourth control circuit for generating the fourth control signal.

[0087] According to one aspect of the present disclosure, a power system includes rectifier circuits 2, 2B, and 2C, a power conversion circuit that receives output power from the rectifier circuits 2, 2B, and 2C and converts at least one of voltage, frequency, and power factor, and a load device 5 that operates using the output power of the power conversion circuit.

[0088] According to one aspect of the present disclosure, there is provided a control method for a rectifier circuit 2, 2B, 2C including first and second input terminals P1, P2, first and second output terminals P4, P3, first to fourth switching elements, and first and second control circuits 11, 12. The first switching element Q1 is connected between the first input terminal P1 and the first output terminal P4. The second switching element Q2 is connected between the second input terminal P2 and the first output terminal P4. The third switching element is connected between the first input terminal P1 and the second output terminal P3. The fourth switching element is connected between the second input terminal P2 and the second output terminal P3. The first and second switching elements Q1, Q2 are transistors. A positive or negative voltage is applied to the first and second switching elements Q1, Q2 with respect to the potential of the first output terminal P4. The control method of the rectifier circuit 2 includes generating, by a first control circuit 11, a first control signal for turning on the first switching element Q1 when a negative voltage is applied to the first switching element Q1 and for turning off the first switching element Q1 when a positive voltage is applied to the first switching element Q1; generating, by a second control circuit 12, a second control signal for turning on the second switching element Q2 when a negative voltage is applied to the second switching element Q2 and for turning off the second switching element Q2 when a positive voltage is applied to the second switching element Q2; supplying power for generating the second control signal from the first control circuit 11 to the second control circuit 12 when a positive voltage is applied to the first switching element Q1; and supplying power for generating the first control signal from the second control circuit 12 to the first control circuit 11 when a positive voltage is applied to the second switching element Q2.

[0089] The rectifier circuits according to the various aspects of the present disclosure are applicable to rectifier circuits, power conversion circuits, and power systems that can operate with low loss not only when AC power is input, but also when DC power is input.

[0090] 1 Power supply device 1ac AC power supply device 1dc DC power supply device 2, 2B, 2C Rectifier circuit 3 Power factor correction circuit 4 DC / DC conversion circuit 5 Load device 11 to 14 Control circuit 21-1, 21-2 Internal control circuit 22-1, 22-2 Reference voltage circuit 23-1, 23-2 Comparator C0, C1, C2, C10 Capacitor D1, D2, D21, D22, D33, D34 Diode Ea1, Eb1 Reference voltage source E33, E34 Voltage source MUX1 Multiplexer P1, P2 Input terminal P3, P4 Output terminal Q1 to Q4, Q21, Q22 Transistor R21 Resistor ZD21 Zener diode

Claims

1. A power supply comprising first and second input terminals, first and second output terminals, first to fourth switching elements, and first and second control circuits, wherein the first switching element is connected between the first input terminal and the first output terminal, the second switching element is connected between the second input terminal and the first output terminal, the third switching element is connected between the first input terminal and the second output terminal, and the fourth switching element is connected between the second input terminal and the second output terminal, the first and second switching elements are transistors, and a positive or negative voltage is applied to the first and second switching elements with respect to the potential of the first output terminal, and the first control circuit generates a first control signal for turning on the first switching element when a negative voltage is applied to the first switching element and for turning off the first switching element when a positive voltage is applied to the first switching element, a second control circuit that generates a second control signal for turning on the second switching element when a negative voltage is applied to the second switching element and for turning off the second switching element when a positive voltage is applied to the second switching element; a first control circuit that supplies power to the second control circuit for generating the second control signal when a positive voltage is applied to the first switching element; and a second control circuit that supplies power to the first control circuit for generating the first control signal when a positive voltage is applied to the second switching element.

2. The rectifier circuit according to claim 1, further comprising a capacitor connected to both the first and second control circuits, the capacitor temporarily storing power for generating the first and second control signals.

3. A rectifier circuit according to claim 1 or 2, wherein the third switching element is a first diode having a forward direction from the first input terminal to the second output terminal, and the fourth switching element is a second diode having a forward direction from the second input terminal to the second output terminal.

4. The rectifier circuit according to claim 1 or 2, wherein the third and fourth switching elements are transistors, a positive or negative voltage is applied to the third switching element with respect to the potential of the first input terminal, and a positive or negative voltage is applied to the fourth switching element with respect to the potential of the second input terminal, and the rectifier circuit further comprises: a third control circuit that generates a third control signal for turning on the third switching element when a negative voltage is applied to the third switching element and for turning off the third switching element when a positive voltage is applied to the third switching element; a fourth control circuit that generates a fourth control signal for turning on the fourth switching element when a negative voltage is applied to the fourth switching element and for turning off the fourth switching element when a positive voltage is applied to the fourth switching element; a first power supply that supplies power to the third control circuit for generating the third control signal; and a second power supply that supplies power to the fourth control circuit for generating the fourth control signal.

5. A power system comprising: the rectifier circuit according to claim 1; a power conversion circuit that receives the output power of said rectifier circuit and converts at least one of the voltage, frequency, and power factor; and a load device that operates on the output power of said power conversion circuit.

6. A control method for a rectifier circuit having first and second input terminals, first and second output terminals, first to fourth switching elements, and first and second control circuits, wherein the first switching element is connected between the first input terminal and the first output terminal, the second switching element is connected between the second input terminal and the first output terminal, the third switching element is connected between the first input terminal and the second output terminal, and the fourth switching element is connected between the second input terminal and the second output terminal, the first and second switching elements are transistors, and a positive or negative voltage is applied to the first and second switching elements with respect to the potential of the first output terminal, and the control method for the rectifier circuit comprises generating, by the first control circuit, a first control signal for turning on the first switching element when a negative voltage is applied to the first switching element, and for turning off the first switching element when a positive voltage is applied to the first switching element; A control method for a rectifier circuit, comprising: generating, by the second control circuit, a second control signal for turning on the second switching element when a negative voltage is applied to the second switching element and for turning off the second switching element when a positive voltage is applied to the second switching element; supplying power for generating the second control signal from the first control circuit to the second control circuit when a positive voltage is applied to the first switching element; and supplying power for generating the first control signal from the second control circuit to the first control circuit when a positive voltage is applied to the second switching element.

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